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My tether spool

(Tim Pierce) #1

Now that the ROV is electrically mostly functional, It’s time to work on the other end. Here is my take on a tether spool so far, based off a Technec Jackreel-f4. i found that I had just enough run in the center hub to run the static wire of the slipring down the center without impacting the bearing surfaces as long as I included a 3d printed spacer to move it forward a bit.

With the cable now on the same side as the static carrying handle, I printed a mount box that guards the wires and holds both the tether interface board and the analog Video balun for the secondary cameras, along with room for additional improvements. I didn’t forget the USB connection, I just have no idea where I am going to put it because the panel mount USB thing isn’t here yet.

there is one additional piece that is not yet there, and thats the tether payout bearing guide. It’s going to mount off the upper handle, and will either be a simple ring, or a 4 roller bearing arrangement. i’m leaning towards the latter at the moment. I’m also thinking of some sort of mounting clamp for the spool, but i’m not sure it’s strong enough as it is to take the strain anyways if a great white decides to eat my ROV and run with it. My fear is that the tether cable with the Kevlar reinforcement IS though.

It’s getting there though!

Slip ring question
Tether Spool/Reel

Looks interesting Tim… but what is going on with that TAZ printer (it looks a lot like one)? Did you hack it to make a feed mechanism?

(Tim Pierce) #3

The Taz printer is another one of my projects. Out on the rest of the internet, I’m mainly known for my 3d printer designs, specifically my Taz modifications. (and the odd 3d printable cello or two) . It just happens to make an interesting place to take pictures of things.

That started out life as a Taz 3 printer, I’ve since highly modified it using Openbuilds extrusions and a bunch of other projects. You can see a rundown of most of the modifications in this video I did about them a few months back. https://www.youtube.com/watch?v=8FlzSqXLnjM . The end result has been what I believe to be the most accurate, fast and precise Taz printer in existence (and one of the most best FDM printers out there period). Though I do need to replace the bed surface at the moment. The tether box for example was printed at 150mm per second federate, which I use when I want to print something quickly for prototyping and I don’t particularly care about the final finish.

Here are all the main modification projects of my own design.

The rest of the designs are here:


Wow, thanks for the explanation! I have a TAZ 5 so it looked familiar.

(Tim Pierce) #5

Finished the initial prototype of the wire roller thingy (fairlead?) it bolts on to the handle., and it seems to be quite strong so far. If there is enough tether strain to break it I have bigger problems, and i’d rather it break than the handle at that point anyways. The brass rods will be stainless once the correct size tube gets here. Takes 6 13mm OD bearings, a bunch of m4 bolts, some M3 bolts and heat set inserts, and some nuts.

Next up, the USB and network cable strain relief velro holder piece. and Lid version 2 with the mini USB in it and a “water resistance in theory maybe” flap. Then I’ll release the files so people can build their own. There will also be a cable stop piece of some sort and some “roll up the last 2 feet of the tether with the anchor point” holders outside the spool so that section doesn’t end up scratching up the tether wires. Those bits won’t take long to make though,

(Tim Pierce) #6

I’ve decided to try and waterproof the electrical box. I have a waterproof ethernet pass through jack and a waterproof USB mini panel mount on the way. It looks like no one makes a waterproof rca jack anymore, and I have to pot the rivet mount points anyways (no idea how I’m getting those out) so my plan is to add a thin epoxy retention slide in divider internally, and extend the top face up and pot the balun in place at the same time. That, coupled with a large groove for rtv silicone gasket material should waterproof most of the case . A replacement cover for the reel side and more gasket material there should take care of most of that, and some potting in the reel cable gland will finish that off. I may add a seacon cable disconnect at that end as well, not because it really needs it, but I’d I have seacon ends on both ends, I can theoretically join two sections later when I can afford another segment. Next I just need a cable segment longer than 3 feet!

Tether quick connect?
(undersearobotics.com) #7

I can tell you how Deep Trekker “waterproofs” the RCA jack that’s on their topside controller: they add a healthy sized “blob” of silicone caulking on the inside (where the female connector solders to wires) of the connector. Not the ideal solution but might prevent some / most splashes from entering the box.

(Tim Pierce) #8

Those balun connectors are about a dollar each, so I think i’m ok with permanently affixing them into the box with epoxy at the top I think. The downside would be that replacing a failed connector would mean a new box essentially, but those things also rarely fail.

(Tim Pierce) #9

The stainless steel tubes I ordered 21 days ago finally showed up, so I did some more work on the tether in preperation for the actual tether cable arriving tomorrow. I now have a “waterproof” tether interface box. I reworked the existing tether box to add a gasket material track, potting areas, and two IP-67 rated network and mini USB interface boxes, to hopefully create an IP-IDK (I don’t know?) rated box. I did want to see the indicators for the board, so the box contains two tiny holes in the lid with wells intended to be filled with clear epoxy. I think it will work? There will also be a variant of the lid with no holes on the final file release.

The rollers are fitted with the new stainless bits, and I added a “drip loop” velcro bundle to the side of the handle, and totally not because “I accidentally stuck the rollers on the wrong side the first time and this makes it look like I drilled those holes on purpose”

There are 3 additional pieces in the works. A set of secondary spooling thingies to wrap the end of the cable with the cable pull, potted join and seacon connection around outside the main spool, a center “stick something attached to a drill in this hole and turn the drill on to roll the tether up quicker” thing (maybe with gears around the outer edge for a future powered tether feed adaptor? and a small piece around the hole in the back of the frame to facilitate potting around the penetration there. I plan on tossing a couple of extra sections of bluerobotics ROV float foam into the center of the round section to keep the unit floating in the event the potting and sealing fails. Though that will probably only work if most of the tether is paid out at the time it goes in the water. Either way there is room and nothing else is going in there, so why not?

To join the lid to the main frame, it uses 4 m3 bolts and heat set inserts, but the waterproofing will be done with clear silicon or RTV or something along those lines. The RCA balun goes in its container, gets filled with goo, then the lid acts as the finishing segment for the outer gasket channel. The 3 screws that hold the box to the reel also get insert panels and then filled with goo after the box is installed. Then the lid goes on. The mini USB connector is waterproof in its own right, the netowrk cable requires either the available lid that it comes with, or the cable in place. Otherwise it is permeable. but it’s the only one I could find.

I do need to figure out a waterproof 2 pin connector of some sort to add a header for a future USBL water gps cable. The plan is to someday build a lower box for that, but as I likely won’t have one of those for years, I can ignore it for now.

I’ll also be making a 3d printable cable join potting box that will hopefully be much smaller than all the commercially available ones I could find. since a 1 inch diameter cable join for a 1/4" cable is completely overkill in this case.

anyways, here are some updated pictures!

I think it’s going to work!

(Tim Pierce) #10

So it turns out the length of tether I purchased is too long to fit on this spool. So I’m now on plan b. This design would work well for a smaller tether though

(Tim Pierce) #11

Ok, plan b acquired. Turns out that a company called schilling makes these reels and they have two larger sizes, the gt380 or the gt410. More expensive, but it should still work about the same.

I grabbed a gt380, well see if that fits.

(undersearobotics.com) #12

How long is your tether?

(Tim Pierce) #13

75m , which appears to be about 15m too long to fit on the first spool,

(Tim Pierce) #14

I went ahead and published the part files for this here: http://www.thingiverse.com/thing:2293622

It is under a non commercial license, if anyone would like to produce these commercially, a commercial license is also available.

(Tim Pierce) #15

I recieved the larger Schill Gt380 spool yesterday. It is about 5 inches wider, 3 inches taller and 5 inches deeper than the jackreel 4, and looks like it will have plenty of space for the cable (or even a 100 meter cable). The box I designed is going to be too small to fit. so I will scale that up to match the new spacing. Its about 1 inch wider. Since I’m going to be redoing it anyways I’ll probably add 2 pair waterproof ports for the Acoustic locator and a future 2 wires for some sort of sonar signal. No idea what connector i’ll use for thhose. If anyone has a suggestion for one to propose as a standard let me know

(Tim Pierce) #16

I finished up the ROV end of the tether assembly this weekend. I also mounted the slip ring. It turns out that the GT380 has a !@#$%^ solid mild steel shaft instead of the hollow one that the jackreel 4 has, but i was able to drill through it with a set of carbide bits. I also got the new back box mounted. It’s about 40mm wider and 30 taller than the other one. I still need to make a new lid for it.

I did discover that ABS plastic sticks extremely well to most kinds of scotchcast casting material. Hence the need for the blue heat shrink wrap. I’m pretty happy with it so far though aside from that. I think with some sort of mold release the 3d printed mold would work just fine.

Tether potting mold?
(Tim Pierce) #17

Made some major progress on the tether spool finally. it’s electrically complete. I just need to print the lid out, pot everything and it will be ready for a dive. I’ll post the finished pictures and links to the project files at that time. The tether on there is a 75m version. I think you could get 100m on there easily without too much issue.

I elected not to have a quick disconnect at the base of the spool at this time. In the future I may put another seacon connector there so I can theoretically add additional tether segments, but I don’t forsee swapping the base reel out enough to make the expense worthwhile.

The final lid design will be similar to the smaller box lid, with the addition of a 2 wire connector for the USBL thingy in hopes that It will someday drop to about 1/3rd the price.

(Tim Pierce) #18

I finally finished up the tether spool. It’s electrically and physically complete, tested and ready for the near future when I have the front lighting hull on my ROV done. The project files and instructions for making your own are available here: https://www.thingiverse.com/thing:2353361 This version will hold approximately 100m worth of cable. I’m definitely happy with it so far. I may make an additional “clampy thing” to clamp the legs to a dock or a boat at some point, as well as a power wind up key (or possibly even a stepper motor controlled feed gear with a tether feed and retract button? I haven’t got that far yet though. At any rate this will probably be the last post with new design stuff in this particular thread for a while. I need to get the ROV done and tested next.

Dry side electronics
(Kevin) #19

@piercet Well, the time has come and I need a tether reel so I am not lugging around 100m of tether on my shoulder. This reel is excellent because it matches my side scan cable reel. I’m buying up parts right now and printing stuff out. I’ll let you know if I get stuck, but thanks for the files and the thorough instructions!

(Tim Pierce) #20

You’re welcome! let me know if you think of any additions you would want, or any changes that would improve it. I’m still really happy with how it came out so far.